Fair. Crystals are exceptionally good at creating straight lines in spite of how hard it is to do so. And you can mimic it macroscopically with scenarios like p

Fair. Crystals are exceptionally good at creating straight lines in spite of how hard it is to do so. And you can mimic it macroscopically with scenarios like piles of uniform spheres, which will form very long straight lines. So yes, not universally true that you need active control to maintain a straight line - some systems passively produce them (another example is folding - when you crease paper the crease wants to continue straight, not curve).